Surgery – Instruments – Orthopedic instrumentation
Patent
1996-02-13
1998-02-03
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 86, A61B 1792
Patent
active
057139067
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device for removing endoprostheses having a shaft engaged in a bone cavity and coupled therein to the bone by a boundary layer made of bone tissue, connective tissue and/or cement.
Endoprostheses of this type are mainly hip prostheses, knee prostheses, elbow prostheses, shoulder prostheses, and ankle prostheses. The prostheses may for instance be mounted in the bone by using a cement such as polymethylmethacrylate (PMMA) or be mounted without using cement. When using cement-free prostheses the shaft of the prosthesis has a surface structure into which the bone tissue in the form of spongiosa is incorporated, thereby forming a solid connection between the bone and the prosthesis. On the other hand, after a certain time there is often a loosening of the prosthesis, due for instance to implantation errors, to short- or long-time infections or to fracturing of the prosthesis or bone. The durability of a first implant is typically ten to twenty years in the case of hip prostheses, in the case of knee prostheses approximately five to ten years. In the case of loosening a revision of the prosthesis is necessary. For this, the prosthesis has to be cut off from its anchoring in the bone cavity and pulled out of its anchoring. To this end, it is known to grip the prosthesis at its free proximal end or in holding means (e.g. holes) especially provided for this, and to remove the prosthesis, for instance by striking with a hammer. Especially in the case of cement-free endoprostheses this process of removal is very difficult, since the connection of the prosthesis to the bone is effected by a multitude of thin spongiosa, each of which may have a small strength, the entirety of which may often make a removal impossible, though. In these cases, but also in cases in which a part of the cement encasing is still strong when using cemented endoprostheses, the bone has to be split or fenestrated in order to weaken its connection to the prosthesis, before the prosthesis may be removed. These mechanical operations lead to a significant trauma of the bone bearing up to fracturing, which makes the revision of the prosthesis difficult and which prolongs the recuperation. This holds even more so for the renewal of revision prostheses, which are longer than the primary prostheses, and during the first revision of which there may already have occurred a loss of bone matter.
SUMMARY OF THE INVENTION
Based on this, it is the object of the invention to develop a device of the type described above, with which the prostheses can be removed while causing as little trauma as possible, so that the removal of the prostheses may be performed simply and with little force.
In order to achieve this object, the combination of features of patent claim 1 is suggested. Advantageous embodiments and further developments of the invention result from the dependent claims.
The solution according to the invention is based on the idea that by driving a flexible chisel blade into the boundary layer between the endoprosthesis and the bone bearing the chisel blade may be guided such that it runs precisely along the surface of the prosthesis, without entering and damaging the surrounding bone or becoming wedged with the prosthesis. The boundary layer consisting of spongiosa or connective tissue structures or cement is separated during this, so that after repeated driving in-over the circumference of the prosthesis the desired removal results. In order to make this possible, the removing device according to the invention has a body having an impact surface on its front face, an elongated chisel blade having a cutting edge at its front end which is guided in a thrust slide of the body and is disposed longitudinally slidable beyond the front face of the body, and a driving-in member which is removably coupleable to the chisel blade and longitudinally slidable along the body parallel to the thrust slide.
According to a preferred embodiment of the invention the chisel blade is made of a flexible flat strip o
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patent: 2655921 (1953-10-01), Haboush
patent: 3803667 (1974-04-01), Rose
patent: 4586496 (1986-05-01), Keller
patent: 4905374 (1990-03-01), Schlein
patent: 5019083 (1991-05-01), Klapper
Ahrens Thorsten
Grothues-Spork Matthias
Scholz Clemens
Buiz Michael
Reip David O.
Ueth & Haug GmbH
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